A conventional aluminum tube having an integral outlet mouth is produced by an impact extruding method (impact press). In this method, a disk-shaped aluminum slug punched out of a rolled aluminum plate (having a purity of 99.7% or higher) is used as a material. The slug is put in a die, and pressed by moving a punch toward the die thereby to be instantaneously extruded through a gap defined between the punch and the die owing to its ductility. Thus, the tube is formed. The aluminum tube has the following advantages:    (1) The aluminum tube is excellent in flavor maintaining property and suitable for long-term preservation of contents in the tube, because it is impervious to air and light.    (2) After the contents are squeezed out of the tube, the contents are not sucked back into the tube (with no back flow of air), so that the remaining contents are less likely to contact the air. Therefore, the aluminum tube ensures that the contents maintain a highly stable quality.    (3) The aluminum tube has no seam, so that print can be provided over the entire outer surface of the tube.    (4) The residual amount of the content can easily be detected during use.    (5) With the use of a transparent ink, excellent print can be provided on the tube, taking advantage of the metallic luster of aluminum.
It has been considered that the die and the tube to be formed should each have a circular cross section. This is because the aluminum slug as the material is circular as seen from a front side thereof and is required to be uniformly extruded through the gap defined between the punch and the die circumferentially of the punch for improvement of yield and for reduction of a material loss. Further, it has also been considered impossible to properly handle a metal tube having a noncircular cross section after the press.
Where a tube having an oval cross section is required for improving the design of the tube and increasing the volume of the tube, a plastic tube such as disclosed in Japanese Unexamined Utility Model No. 64-51040 (1989) is used.